1. Field of the Invention
The present invention relates to a printing apparatus in which when printing is performed, a printhead is pressed against a platen with a print medium sandwiched between the platen and print medium.
2. Description of the Related Art
A wire dot printer has been widely used and is used in recent Point of Sales system (POS system) to print on a multi-part journal paper and single sheets. In order to print on two different types of print paper, the POS system has two paths for transporting two types of print paper.
FIG. 27 illustrates a POS printer that prints on two different types of print paper.
FIG. 28 illustrates the POS printer that prints on a multi-part journal paper 7.
Referring to FIG. 27, a platen 2 is disposed to oppose a printhead 1. Disposed behind the platen 2 are a roll of journal paper 3 and a roll of receipt paper 4 that are ready to advance to a printing area. These two types of print paper are transported to the printhead 1 for printing. The POS printer also prints on another single sheet 5, which is transported to the printing area from under the printhead 1 for printing.
For POS printers, the single sheets 5 take the form of slip paper or check paper. When printing is performed on the single sheet 5, the printing is carried out with the single sheet 5 in direct contact with the journal paper 3 or receipt paper 4 if the journal paper 3 or the receipt paper 4 has been loaded on the platen 2. Moreover, as shown in FIG. 28, a similar case would occur if the multi-part journal paper 7 has been loaded on the platen 2.
FIG. 29 illustrates a problem with the conventional platen 2.
With the aforementioned conventional printer, when printing is performed on a single sheet 5 with the journal paper 3 or receipt paper 4 loaded at the printing area, the printhead 1 is moved relative to the single sheet 5 in a direction shown by arrow C. There is a gap 6 between the journal paper 3 and receipt paper 4 as shown in FIG. 29. Thus, the pins of the printhead 1 are apt to scratch the single sheet 5 at the gap 6. An additional problem is that printing results may not be sufficient in density at an area where the printhead 1 faces the gap 6.
FIG. 30 illustrates another problem with the conventional platen.
When printing is performed on the single sheet 5 with multi-part journal paper 7 loaded at the printing area, printing is carried out with the single sheet placed over the multi-part journal paper 7 as shown in FIG. 30. This way of printing wastes the multi-part journal paper 7, increasing the running cost of the multi-part journal paper 7.
The present invention was made in view of the aforementioned drawbacks of the conventional apparatus.
A platen having an impact surface positioned to oppose a printhead so that a part of a printhead strikes a print medium loaded on the impact surface. The platen comprises a first impact surface having a curved surface, a second impact surface having a curved surface, and an opening formed between the first and second impact surfaces. A print medium advances into the platen and passes through the opening from an inside of the platen to outside of the platen so that the print medium extends to cover one of the first and second impact surfaces. The platen is movable such that the first and second impact surfaces are selectively positioned to oppose the printhead.
The platen is rotatable about an axis and the first impact surface has a first curvature with respect to the axis and the second impact surface has a second curvature with respect to the axis.
A printing apparatus has an impact surface positioned to oppose a printhead so that the pins of a printhead strike a print medium against the impact surface. The apparatus comprises a plurality of impact surfaces used for printing different types of print medium supplied through different paths. Each of the plurality of impact surfaces is used for a corresponding type of print medium. A drive means causes the plurality of impact surfaces to selectively oppose the printhead so that print data is printed on one of the different types of print medium located between a corresponding one of the plurality of impact surfaces and the printhead.
The printing apparatus may further have an opening through which one of the different types of print medium passes, the opening being formed in a platen between adjacent ones of the plurality of impact surfaces.
The printing apparatus may be constructed such that the plurality of impact surfaces have curved surfaces with different curvatures.
The printing apparatus may be constructed such that the plurality of impact surfaces are made of a material different from other part of the platen.
The printing apparatus may further include means that holds the platen in position when one of the plurality of impact surfaces opposes the printhead.
The printing apparatus may have a projection formed on one of the plurality of impact surfaces. The projection extends in a direction substantially perpendicular to a direction in which the one of the different types of print medium advances. The projection is substantially configured to the flection of the one of the different types of print medium advances.
One of the plurality of impact surfaces of the printing apparatus is driven to selectively rotate about an axis to a first position and a second position. The first position is such that the at least one of the plurality of impact surfaces directly opposes the printhead. The second position is such that the at least one of the plurality of impact surfaces does not oppose the printhead. The plurality of impact surfaces are aligned with the printhead such that when the at least one of the plurality of impact surfaces rotates from the first position to the second position, the drive means causes an impact surface adjacent to the at least one of the plurality of impact surfaces to move closer to the printhead for printing.